The Best Kind of Darkness
by IWriteSins-NotFanfictions
Summary: Dean knows he has to resist the power of the Mark of Cain, even if it kills him. What better way was there to do it than with Castiel? (Rated T for language)


Descent into Darkness

Summary: Dean knows he has to resist the power of the Mark of Cain, even if it kills him. What better way was there to do it than with Castiel?

Information: Written post 10x05 / Fan Fiction. Spoilers through then (specifically season ten).

The Mark of Cain was the equivalent of a bratty toddler that was throwing a tantrum because Dean wasn't paying attention to it.

That's how it started, anyway. An annoyance, for sure, but something that Dean could ignore when he kept his mind occupied by a hunt, or research, or even when he was just slightly buzzed. Now, however, it had begun to pulse with need. The Mark had its own heartbeat that Dean found he could not ignore no matter how he tried.

_Kill. Kill. Kill. _

As the Mark grew more demanding, Dean's demeanor decreased accordingly. It had started out simply, with him just getting annoyed over the simplest things. Sam tapping his foot against the floor. Traffic moving far too slowly. Staining his favorite TV shirt with blood. His best friend being M.I.A since Dean was cured of his demon-ness. Sam's teasing about all things "Deestiel" since they attended their musical. Things like that.

Sam seemed to sense Dean's state, as he wisely left him alone when he was in one of his 'moods.' He knew that Sam was doing his best to research about a cure for the Mark, but Dean knew that the entire matter was likely to be useless. There was no cure, Dean had known that even as Cain has given it to him. The Mark was a means to an end – and he had managed to end Abbadon's life. Not Metatron's though, as he had hoped.

Soon the Mark began to haunt his dreams as well. He dreamed of the kill. He dreamed of finding the First Blade, wherever that bastard Crowley had hidden it, and using it to end the nearest creature he could find. The pleasing feel as the blade connected with flesh and tore away at skin. The warm blood gushing out of the wound as Dean watched the light leave his victim's eyes. That's when he would usually awaken in a cold sweat, hyperaware of the Mark pulsating with desire.

He was so, so close to snapping and yet there had been no serious supernatural attacks recently. He had dealt with Kate and Tasha, but had no reason to kill Kate after she had taken care of her wayward sister. Dean wasn't about to snap on some poor, innocent soul, no matter how desperate he was. So while Sam did his research, Dean scoured the newspapers for any sign of anything supernatural that he could kill to relieve the ache. He even considered for a few moments wandering the streets to find the nearest scumbag and end their life. Killing humans, of course, was something else entirely to Dean – something he hadn't been comfortable with after becoming human again.

It was when the thought of killing Sam crossed his mind that Dean knew that he was screwed. He was terrified of waking up from one of his dreams of killing someone he cared about – Sam or Cas, specifically – and realizing that it hadn't been a dream.

Dean knew what he had to do. He had no idea if it would work, but he would be damned if he didn't at least try. Acting methodically, he quickly wrote Sam a note – _Went to go take care of something. Be back sometime tomorrow. Dean – _and packed himself a bag of essentials. After managing to sneak out of the bunker he drove until he happened upon a random motel.

_Kill. Kill. Kill. KILL. _

After resisting the urge to snap the neck of the man who gave him his room key, Dean managed to find himself in a room that he had boarded up as much as possible to make it harder for him to leave. After warding the room against some of the more common creatures, he fell upon the bed as a new wave of pain coursed through his arm and spread through his body. The throbbing had increased to a dull pain, not dissimilar to the feeling of a toothache. The Mark seemed to know about his resistance and was responding by making itself more known.

Grabbing a pair of binding handcuffs from his bag, he attached one part to his right wrist and the other half the bed post. The Mark didn't like that. Another wave of pain crashed through Dean's body and he closed his eyes against the assault, waiting for it to subside. After what seemed like a lifetime the pain lessened and Dean was able to open his eyes.

He briefly wondered if the Mark would kill him if he didn't follow through. If the Mark did try to kill him, would he become a demon again? Neither of those outcomes were particularly appealing. Dean cursed Crowley in his head, but ultimately knew that it was his own damn fault for not listening to Cain when he told him about the side effects. Would he have resisted the Mark, even if he had listened?

He let his mind wander as he stared up at the ceiling. For once, heaven and or hell weren't dicking around with him or his brother. It had almost felt like years ago, a more innocent time. Before he had to trade his life for Sam's from the crossroad demon. Before he had gone to Hell. Back to a time when all of his problems could generally go away with an exorcism and a gun.

Before he even knew that angels had existed. Before he had even heard of an angel named Castiel.

He didn't regret anything about those years, to tell the truth. He never regretted that initial deal with the crossroad demon despite everything that had occurred with it. What was the other option? To let Sam die? Fat freaking chance.

He winced as another bout of pain coursed through his arm, squeezing his eyes shut. It felt as if he had stuck his arm in a fire but couldn't move it to get it out. He jerked involuntarily, straining against his restraints as he bit down on his lip. It was all he could do to stop himself from screaming out in agony. Worse yet were the memories that flashed in front of his eyes – memories of Hell, of torture and being tortured, of yellow and black eyes.

_Kill, Winchester. I know you want to. _

As the pain finally began to subside he slowly reopened his eyes. Breathing heavily, he looked up at the headboard and felt something like horror seize his chest. The end of the bed, the only thing that was keeping him from tearing his way out of the room, was beginning to crack. A few more strong tugs and Dean could be free.

"Fuckfuckfuckfuckfuckfuckfuck," he groaned aloud vehemently. It couldn't break. He couldn't leave the room, unless he wanted to be tied to a rampage that took the lives of everyone in this godforsaken motel. Part of him knew what he wanted – needed – to do. Call Castiel. The other part of him thought that that was one of the stupidest ideas he ever had. There was no way that Dean was letting Cas see him like this, so out of sorts, so not-Dean Winchester.

"_Well, he's seen you as a demon," _Dean mused to himself. _"Is this really any worse than that?" _

He paused for a moment, considering the notion that, at that point, he had no other choice. That was when the thought struck him. There was still the fact that Castiel wasn't back up to one hundred percent yet. What would happen if Dean attacked him? He couldn't live with himself if he managed to hurt Cas. The thought of killing him was even more nauseating.

Realizing he likely had no other options as the Mark started another agonizing assault, he gritted his teeth and began to pray aloud.

"Cas, if you can hear me…can you…wing yourself here?" The room was silent besides the sound of Dean's own labored breathing. "Please, Castiel. If you can hear me. I need you."

As the pain seemed to increase Dean closed his eyes, doing everything he could not to break the rest of the headboard. He knew that if he didn't keep gritting his teeth then the entire motel would have been able to hear his screams of agony. More images flashed in his mind. Holding Sam as he died in his arms. The echo of his mother's screams as she burned upon the ceiling. Seeing Castiel on the ground, majestic angel wings burning their mark upon the ground.

The pain died down again eventually, though Dean noticed each wave of pain was getting longer and more intense.

"Dean."

Dean opened his eyes back up to look at the man who stood before him. There was a part of Dean that almost wanted to weep in relief that Cas had shown up. Castiel regarded him with the same somber expression that Dean had become accustomed to, but Dean could see an unusual tightness in his eyes.

"Cas… Thank you," Dean managed to breathe out. "I wasn't sure if you'd come."

"I'll always call when you come," Castiel said seriously, still staring at him. In the beginning Cas' stares had unnerved, even bothered Dean, but now they had become such commonplace that they seemed natural. Dean stared back, taking in the angel's appearance. His hair was just slightly disheveled, his trench coat marred with a smattering of what looked like fresh blood. His cheek was sporting a small gash that looked relatively new.

"Cas, are you okay?" Dean asked, alarmed. Castiel seemed bemused by something as he looked down at his appearance.

"Perhaps I should be the one that is asking you that," he responded carefully, nodding just slightly toward the handcuffs.

Dean sighed, and gestured towards the bed for Castiel to sit down. After a brief moment of hesitation he sat down next to Dean, crossing his legs over and pulling them close to his body. The sight was almost comical, so human. Dean would have laughed if he hadn't been in so much pain. He briefly wondered if he should feel uncomfortable about their close proximity, but decided that he ultimately didn't care. Personal space had gone out the window years ago.

"Dean," Castiel demanded seriously. "Tell me what's going on and why you called me here."

"The Mark," Dean replied gravely. "It's getting worse. Has been for a while now." He paused, collecting his thoughts. "I could probably find something to kill to appease it, but I'm sure I'd just go through the same thing again. I'm hoping that if I manage to ride this out then the Mark won't have as much power over me."

Castiel nodded, silent, considering the information.

"Or kill me," Dean added, suddenly, quietly.

Castiel nodded again, though Dean noted the barest of twitches in his jaw. Cas sat silently for an indeterminable amount of time and Dean wondered if he had even heard him.

"Again," Castiel finally stated.

Dean blinked then, realizing Cas was making a joke, chuckled. "Yeah, again. How many times does that make it? One hundred?"

"Probably more," Castiel mused, finally cracking the barest hint of a smile. "You Winchesters sure do keep heaven and hell busy."

Dean finally smiled, for the first time in what felt like ages, but his smile quickly turned into a grimace as The Mark made itself known again. He gripped the sheets with his free hand, biting his lip again.

_Kill him. _

"Fuck you," Dean hissed aloud. Time passed, the pain receded again and Dean noted that a hand was covering his free one. He finally opened his eyes to meet Castiel's baby blues. Dean saw some deep seated emotion resting there, but couldn't quite determine what it was. He waited a moment before moving is hand out from under Castiel's, instantly missing the warmth and comfort of his companion.

"I need you to make sure," Dean whispered eventually. "That I don't get out of this room. No matter how much pain I'm in. No matter how I beg and plead." He paused, again collecting his thoughts. "If you don't want to do it, I understand. You can leave. There's a note in my bag though that I wrote for Sam though," Dean gestured to the bag with his head. "Do you think you could give it to him?"

"No," Castiel said determinedly.

Dean cocked an eyebrow at him and noticed how…_intense_ Cas' features were. He was almost angry. He could have drowned in the emotion that Castiel exhibited, so rare in his angel friend, that he found himself staring.

"You can give the note to Sam yourself, tomorrow," he declared, and Dean felt the oddest hitch in his breath.

Dean briefly felt worry flare up again as he wondering about the extent of the Mark's power. Could it eventually take over? He wondered if he began to feel the Mark taking over, would he have the strength to tell Cas to leave. He wondered if he did tell Cas to leave, would Cas comply. He bit his lip again, wondering if he had made a horrible mistake by asking Castiel to come here.

"Cas…" he began.

"Why did you ask me to come here, Dean?"

The first thoughts in his mind were _"I didn't want to risk Sam's life" _and _"I didn't want to be alone tonight," _but as he thought about it he wondered if there wasn't something deeper.

"Stupid subtext," Dean muttered as Cas raised an eyebrow at him. Probably wondering if he was still insane.

"I don't know," Dean admitted eventually. "I just know that if this is my last night on Earth, spending it with you wouldn't be the worst thing."

Dean suddenly really wished he had a drink in his hand as he felt his face warm up. _"Way to be a chick, man."_

Another smile flickered across Castiel's face, and Dean marveled again at how much Cas had changed over the years. He used to be this stoic, unyielding man and now he displayed emotion and feeling that were akin to a human. Dean liked to think that he perhaps played a part in the transformation.

A bout of pain pulsated from the Mark, and Dean felt himself grabbing at… something. His hand, clenched, met Castiel's and dug into his palm. He was thankful that Castiel's pain tolerance was so high, Dean felt at that moment that he could have ripped Cas' hand off in his torment. His eyes closed, seeking a refuge that the world refused to give him.

_"They're getting worse,"_ Dean thought, barely able to think coherently.

Just as they all had before the pain finally subsided. Dean exhaled a breath he didn't know that he'd been holding. He felt a weight on his chest shift and snapped open his eyes to once again meet Cas's blues. Cas had taken it upon himself to lay on top of Dean, one of his hands laying on Dean's heart and the other still holding Dean's hand. His legs had tangled with Dean's in a vice grip, presumably to hold him in place. Dean realized, with a rush of blood to his face, that Castiel's hand was on top of his heart. It all seemed so _intimate._

"Cas?" Dean asked, his voice rougher than he intended.

"Yes, Dean?" Castiel replied innocently.

"Why are you lying on top of me?"

Castiel rolled his eyes, as if exasperated with the human. Dean briefly wondered where Castiel had picked up that gesture.

"By whatever means necessary, Dean."

"Right," was all Dean could think to reply. He took comfort in the knowledge that Castiel didn't know how compromising their position looked. At least, Dean didn't _think_ Cas knew what it looked like, but of course who knew, considering how long Castiel had spent on Earth. And with the Winchesters no less.

"It's a calming gesture," Castiel continued, chin gesturing to the hand on top of Dean's heart.  
"It helps me to transmit feelings of serenity to you."

"Oh," Dean could only think to respond, suddenly feeling a bit like an ass.

"I could move if –"

Castiel was cut off as another wave pulsed through Dean. He closed his eyes again against the onslaught of _kill kill kill _that coursed through his head and emanated from his body.

"How did you get cut?" Dean managed to force out without biting his tongue off.

Castiel was silent, staring at Dean's taunt face.

"Cas, _please,_ tell me. I need you to distract me."

Castiel wondered how many times he had heard the word _please_ from Dean Winchester, and realized that he rarely used it unless in some kind of great need.

"Hannah and I were…attacked, by fellow angels."

Dean grunted, as if to say _continue. _His eyes still scrunched together, face still a mask of pain. If it meant relieving Dean of any sort of pain then Castiel would do anything.

"It would appear that, after everything, angels still cannot find their peace. There is still fighting among those who wish to stay on Earth and those who feel that it is our obligation to return to Heaven," Castiel shook his head to himself, as if in disbelief at yet more fighting amongst his brothers and sisters. Had it always been this difficult?

"I suppose that that's the ultimate price of free will," Castiel continued solemnly. There will always be those who see differently than yourself and be willing to fight about it."

All at once Dean's face relaxed. He exhaled in relief, but didn't open his eyes yet.

"Shouldn't you be healed by now then? Angel mojo and what not?" Dean asked, voice gruff.

"One would think," Castiel murmured. "It appears my angel 'mojo,' as you call it, is not completely functional. Most likely because it is not my own."

Dean nodded in understanding, finally opening his eyes again. Within them Castiel saw a very broken, very wounded man. He felt something akin to his heart twisting in his chest.

"It'll be okay, Dean," Castiel began, hoping that it could provide at least some semblance of comfort. "I won't let you hurt me or anyone else. I'll stay by you until this mess is over."

"Why?" Dean breathed.

Castiel paused for a moment, considering what Dean just asked, cocking his head to the side. The answer was simple, really.

"What's the matter? Don't you think you deserve to be saved?" Castiel replied, the barest of smiles on his face. Dean couldn't help it, he smiled in return. Castiel shifted suddenly, coming off Dean and laying down next to him instead. Dean felt the oddest sense of loss as Castiel got off of him, even if he did keep his legs intertwined and his hand on Dean's heart.

Castiel moved closer to Dean, almost as if he was snuggling up to him while simultaneously keeping him contained in his vice grip. Dean again felt the rush of blood to his face and proceeded to focus on the ceiling rather than Cas. Ann odd sense of calm washed over Dean, and he wondered at Castiel's mysterious angel abilities as he felt something similar to sleepiness begin to weigh down his eyelids. A gush of air brushed over his face, like being hit by a fan, and then suddenly an odd sense of comfort and warmth, like the lightest blanket in the world.

"Cas?" Dean asked, slowly.

"Yes, Dean?"

"Are those your wings?"

"…Go to sleep, Dean," Castiel commanded.

"If you keep talking. About anything." Dean countered, quietly. He couldn't exactly explain it, but there was something so very comforting about hearing Castiel's voice. It was almost like a lullaby. His problems – the Mark, Metatron, Heaven, Hell – all seemed to melt away. Castiel's voice washed over him, like waves at the beach, as he began telling the story of how the Great Pyramids were built.

As Dean began to drift he felt the oddest sensation on his forehead, like a kiss but barely detectable. It was oddly comforting. He had no idea what would happen when he woke up – if the Mark would be worse for wear or moderately better, but at that moment he couldn't muster up the ability to worry.

Even with the pulsating Mark that reared its head every now and again through the night, Dean couldn't remember sleeping better in years.


End file.
